Astronauts prepare for Wednesday spacewalk at ISS

Published On: Sep 04 2012 01:56:05 PM EDT

Two astronauts are preparing today to venture outside the International Space Station on a spacewalk aimed at restoring electrical power at the outpost Local 6's news partner Florida Today reports.

American astronaut Sunita “Suni” Williams and Akihiko Hoshide of Japan Aerospace Exploration Agency worked inside the U.S. Quest airlock, readying protective spacesuits for their second spacewalk in six days.

Williams and Hoshide aim to install a spare power-switching unit on the central truss of the space station. An initial attempt last Thursday failed when the astronauts were unable to bolt the spare in place.

The 220-pound unit is one of four that route power from the station’s massive American solar arrays to various outpost systems and its laboratories.

Electrical power from two of eight American solar panels cannot be routed to the station until the spare is put in place.

Power from a third solar panel also was lost when a voltage regulator shorted out in an unrelated failure over the weekend.

“So out of the eight channels of power on the International Space Station, from those big giant solar arrays, three of them are suffering some challenges right now,” said NASA mission commentator John Byerly.

Two of those power channels will be restored if Williams and Hoshide can bolt the spare switching in place.

The astronauts were unable to drive the bolt completely into place during the spacewalk last week. Engineers think metal shavings might be contaminating threads, causing the bolt to gall, or freeze up.

Over the weekend, Williams and Hoshide fashioned hand-made tools to clean the bolt and its nut before installation. They’ll have about a three-hour window of opportunity to complete installation on Wednesday. If they can’t get the job done, the power-switching unit will be taken back inside the station for examination.

Engineers also are analyzing the trouble with the voltage regulator. It appears they will be able to reset the regulator with remote-control computer commands.

Flight controllers in the meantime are routing power through the five other channels, and NASA officials say all station systems and research facilities are up and operating.

Williams and Hoshide will start their spacewalk about 7:15 a.m. EDT Wednesday. It is expected to last about 6.5 hours.

The spacewalk will be the 165th performed during the assembly and maintenance of the station. Its first two building blocks were linked in low Earth orbit in December 1998.